A Mn2+-requiring enzyme present in the cytosol of mammalian and microbial cells. In contrast to the mammalian form, the bacterial form of the enzyme (type example of peptidase family S33) hydrolyses both polyproline and prolyl-2-naphthylamide. The mammalian enzyme, which is not specific for prolyl bonds, is possibly identical with EC 3.4.11.1, leucyl aminopeptidase.